First, let's consider some of the factors that make life on our planet possible:
The Earth has a lot of water covering its surface. In fact, water covers over 2/3 of the Earth's surface!

Also, the Earth has a protective atmosphere that shields living things from UV and X-rays, types of light that can harm living things. Some UV rays are able to penetrate the Earth's atmosphere, however, and this is why it is necessary to use sunblock.

The Earth's temperature fluctuates within a given range that sustains life.

The elements that make up living things are found in abundance on Earth, elements such as carbon, hydrogen, nitrogen, oxygen and phosphorous.

The possibility that life exists on other planets is being studied by scientists. They often begin by looking for stars with characteristics similar to our Sun's. There are many factors that researchers must consider as they narrow their search for life on other planets, such as...

- The size of the star around which the planets rotate
- The age of the star
- The size of the planets orbiting the star
- The planets' distance from the star
- The temperature of the star